TaskRunner.StopTask() doesn't terminate child processes

[spaceisfun]

This is most noticable when running programs via the app command prompt, since they are invoked via cmd.exe /C .

NET Core 3.1 has a Kill(true) method to terminate child processes, but it isn't available in NET Standard, yet. It should be with NET 5.0. Or, copy the implementation of Kill() true and reimplement it in our code